Method of coating metals by cementation.



A. SANG" METHOD OF COATING METALS BY QEMENTATION. APPLICATION FILED JAN.2, 1909.

Patented Feb. 8, 1919.

WITNESSES INVENTOR Wm A W MSW w Miff ALFRED sane, or BELLEVUE,PENNSYLVANIA.

METHOD OF COATING METALS BY CEMENTATION.

Specification of Letters Patent.

Application filed January 2, 1909.

Patented Feb. 8, 1910.

Serial No. 470,369.

To all whom it may concern:

'Be it known that I, ALFRED SANG, of Bellevue, Allegheny county,Pennsylvania, have invented a new and useful Method of Coatin Metals byCementation, of which the fol owin is a full, clear, and exactdescription, re erence being had to the accompanying drawing, formingpart of this specification, in which the figure is a longitudinalvertical section of one form of apparatus which may be used in carryingout my invent-ion. Z

My invention has relation to a method of coating metals with othermetals, by cementation; and is designed to provide a novel, simple andeffective method of this character which will largely overcome thedifliculties heretofore experienced in this class of work; which willeffect a large saving of time and heat, and which will reduce the dangerof oxidation of the coating material. I Y

The great drawback heretofore in coating metals by cementation hasconsisted in the fact that the coating metals, which are either in theform of a salt of the metal, an oxid, or an oxidized powder, arenon-conductors, of extremely poor conductors, of both heat andelectricity. This has made it difficult to get theheat through thecoating metal and to get an even distribution of heat at all portions ofthe surface or surfaces to be coated, except after a considerable periodof tinie. The results, even where rotating drums and other meanshavebeen employed to facilitate the distribution of heat, have been veryirregular. My improved method is designed to obviate these diflicultiesby overcoming the resistance of the coating material to the passage ofheat and. by providing a simple and efiicient method whereby a properheating action may be obtained.

In accordance with my invention, I immerse or bury the article orarticles to be treated in the coating material, which is in the usualpowdered form, and when an oxid, or oxidized dust is employed as thecoating material a reducing agent, such as carbon, or better still,carbonic oxid gas is employed, If some other compound of\t he metal isused, suitable reagents are added excepting when the heat alone willreduce'tlie coating material to the proper condition. I then heat thearticle or articles by means of an electric current. This may beaccomplished in the case of pipes, as shown in the accompanying drawing,in which the numeral 2 designates a retort of any suitable character, 3the powdered coating metal or compound of the metals in which thearticle 4 to be coated (such as an iron or steel pipe) is immersed orburied. The pipes 4 are supported .at their ends by terminals 5, whichmay be of conical form, and which pass through non-conducting heads 6,or non-conducting portions of the heads, of the retort, and which areconnected with any suitable source of electric energy (not shown). Thearticle or articles may be quickly brought to the necessary temperatureto bring about the decomposition of the c'oatin material and thedeposition of the coatmg metal upon the article. This temperature willbe substantially uniform throughout the extent of the article, thusinsuring uniformity of result.

When a plurality of articles are to be simultaneously treated, they maybe all buried or immersed in the coating material and connected inmultiple in the heating circuit.

With articles which form good resistances,

and therefore heat up readily, they may be connected in various ways, asby copper conductors of sufficient capacity to prevent undue heatingthereof.

My invention is applicable to the coating of various articles withvarious coating met als, a specific instance being the coating of ironor steel articles with zinc, in which case the zinc used is preferablyin the form of owdered zinc oxid, or zinc dust, the articles beingburied or immersed in the oxid or dust, with a reducin agent, and heatedin the manner describe Where the coating material is a straight metal,the deposition takes place without a reducing agent, but carbon may beadded to prevent oxidation. Where, however, the coating material 1soxidized, as zinc dust, antimony dust,'precipitated copper dust, copperconverter flue dust, and the like, and with the OXldS of these and othermetals, a reducing agent should be employed. Various compounds of themetals may be used, with the addition of a suitable agent or agents fortaking care of the non-metallic elements. I may also use a combinationof difierentmetals which will either unite to form an alloy coating, orwhich will be separately deposited to form a compound coating. Thus, ifcopper dust and zinc dust are employed, a brass coating will bedeposited. In some cases, however, I have noted a separation, or partialseparation of the zinc and copper in the coating, showing or tending toshow a precipitation of copper by the zinc before the zinc is deposited.It will also be obvious that various forms of apparatus may be used tocarry out the invention.

What I claim is: p

1. The method of coating metal with another metal or metals bycementation, which consists in burying or immersing the article to becoated in a metallic coating material, and passing an electric currentthrough the article to heat it to a sufficient temperature to cause thedeposition of the coating material thereon; substantially as described.

2. The method of coating metal with another metal or metals bycementation, which consists in burying or immersing the article to becoated in the metallic coating material, and heating the article by anelectric current, in the resence of a reducing agent, to thereby efl ecta reduction of the coating metal and its deposition upon the surfaces ofthe article to be coated; substantially as described.

3. The method of coating metals with another metal or metals bycementation, which consists in surrounding the article to be coated withthe metallic coating material in finely divided form and with a reducingagent present, and then passing an electric current through the articleas a resistance core to effect a reduction of the coating material andits deposition upon the surfaces of the article to be coated;substantially as described.

4. The method of coating metal with another metal or metals bycementation, which consists in bringing the metal surface of the articleto be coated in contact with the metallic coating material, and thenheating such article by passing an electric currenttherethrough;substantially as described.

In testimony whereof, I have hereunto set GEO. H. PARMELEE.

